1. Field of the Invention
The present invention relates to a flow control device, and more particularly, to a flow control device for controlling a flow of a chemical solution supplied by a supply apparatus.
2. Description of the Prior Art
In a semiconductor manufacturing process, many kinds of chemical solutions are used for cleaning, wet etching processes, etc. In order to precisely control the reactions of these solutions, the flow of the solution must be controlled to satisfy the flow velocity, volume and commixture ratios of the semiconductor process.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a prior art chemical solution supply apparatus 10. The supply apparatus 10 is used to supply a chemical solution 12 for a semiconductor process. The supply apparatus comprises a storage tank 14, a solution transfer device 16, and a pressurizing apparatus 18. The storage tank 14 serves as a reservoir for the chemical solution 12. The pressurizing apparatus 18 supplies high-pressure gas into the storage tank 14 to pressurize the chemical solution 12 and thereby forcing it to flow into a semiconductor processing room (not shown). The solution transfer device 16 is used to route the chemical solution 12 into the processing room. The solution transfer device comprises a chemical flow pipe 20 to route the chemical solution 12, a flow meter 22, a switch valve 24 in series with the chemical flow pipe 20 and a nozzle 26 installed on the end of the chemical flow pipe 20. The flow meter measures the flow of the chemical solution 12. The nozzle 26 uniformly sprays the chemical solution 12.
The pressurizing apparatus 18 comprises a gas input pipe 28 to route high-pressure gas from a high-pressure gas source 30 to the storage tank 14. The pressurizing apparatus also comprises an adjust valve 32 and a gas meter 34 installed in series with the gas input pipe 28 for measuring and adjusting the pressure of the input gas into the storage tank 14 from the gas input pipe 28.
However, in a typical semiconductor factory, for safety and convenience, the pipes for gas and those for liquids are independently installed and operated. During the operation of the prior art supply apparatus 10, the user can only measure and adjust the pressure of the input gas by way of the adjust valve 32 and the gas meter 34. So, during manufacturing operations, the pressure of the gas in the gas input pipe 28 holds a constant value and cannot be adjusted according to the rate of flow of chemical solution 12 as read from the flow meter 22. When the solution transfer device 16 sends the chemical solution 12 into the processing room, the flow of the chemical solution 12 holds a constant value; for example, something like 130 cc/min. The chemical solution 12 used in the semiconductor process could be any combination of corrosive, poisonous or inflammable. Consequently, in the supply apparatus 10, the chemical flow pipe 20 is made of a plastic material, and the installation of any intrusive mechanical or electrical equipment in the pipe is avoided in order to ensure a continuous seal along its length and to reduce the possibility of combustion or leakage. Therefore, the switch valve 24 has only a simplistic on and off ability, which does not require an intrusive mechanical or electrical apparatus. The only choices for flow control of the chemical solution are, in this example, 130 cc/min and 0 cc/min. If the user wants a different rate of flow (like 60 cc/min), the prior art supply apparatus 10 is unable to satisfy the request.